I remember when I joined Facebook, it was at least in part because it alleviated a lot of the MySpace privacy concerns. It didn't share data with outside companies, and only people with a UVA email address or who I accepted their friend request could see anything beyond my name, school, and photo. If I had known they would eventually be sharing my data such that CNN.com gets it if I just surf there or that it would publish my online shopping habits if I didn't opt-out (thankfully a rescinded policy), I'd have been more hesitant to sign up.